1. Field of the Invention
This invention relates to a positioning device, and more particularly to a spindle positioning device for a pneumatic impact tool.
2. Description of the Related Art
Referring to FIG. 1, a conventional pneumatic impact tool 1 disclosed in US2011/0139474A1 includes: a housing 11; a spindle 12 disposed rotatably in the housing 11 and extending along an X-axis for power transmission; an output shaft 13 disposed rotatably in the housing 11, geared to the spindle 12, and extending along a Z-axis perpendicular to the X-axis for outputting a power; and a bushing 14. The spindle 12 has a position-limiting surface 121 parallel to the Z-axis. The bushing 14 is threaded in the housing 11, and has an end surface or stop surface 141 abutting against the position-limiting surface 121.
As such, when the spindle 12 is driven by a power source (not shown), such as a pneumatic cylinder, to rotate, due to the geared connection between the spindle 12 and the output shaft 13, the output shaft 13 is rotated to output the power. At the same time, the stop surface 141 of the bushing 14 obstructs the position-limiting surface 121 of the spindle 12 to prevent the spindle 12 from moving away from the output shaft 13 along the X-axis.
However, since the bushing 14 is just threaded to the housing 11, during power transmission, the spindle 12 pushes the bushing 14 to move in the housing 11 in a direction away from the output shaft 13 due to reaction force coming from the output shaft 13, thereby resulting in a change to the distance between the spindle 12 and the output shaft 13, which affects adversely smooth rotation of the spindle 12 and the output shaft 13 and reduces the service life of the pneumatic impact tool 1.
To overcome such drawbacks, glue is applied between the bushing 14 and the housing 11 to prevent movement of the bushing 14 in the housing 11. As a result, the spindle 12 and the output shaft 13 cannot be removed for replacement, repair, and maintenance.